Table 2 Association of 1^st ultrasound with AI at age of six months in 338 hips

Normal 1^st ultrasound (with normal /abnormal AI at 6 months)

27 (22/5)

118 (116/2)

Abnormal ultrasound (with normal /abnormal AI at 6 months)

311 (294/17)

220 (200/20)

Sensitivity^a (95%CI)

77% (55–92%)

91% (71–99%)

Specificity^a (95%CI)

7% (4–10%)

37% (31–42%)

Positive predictive value^a (95%CI)

5% (4–7%)

9% (8–10%)

Negative predictive value^a (95%CI)

81% (65–91%)

98% (94–100%)